class Solution {
public:
    int mySqrt(int x)
    {
        if (x == 0)return 0;
        long long left = 1, right = x;
        while (left < right)
        {
            long long mid = left + (right - left + 1) / 2;
            if (mid * mid > x)
                right = mid - 1;
            else
                left = mid;

        }
        return left;


    }
};